Knowledge Resource Center for Ecological Environment in Arid Area
| 黄土高原退耕还林的土壤水分效应研究 | |
| 其他题名 | Study on soil water effects of returning farmland to forest on the Loess Plateau of China |
| 张晨成 | |
| 出版年 | 2017 |
| 学位类型 | 博士 |
| 导师 | 邵明安 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 近年来黄土高原大规模的退耕还林使得该区成为我国植被变化最剧烈的地区。然而，不合理的植被建设使植被生长与土壤供水能力负反馈，形成土壤干层，出现人工林退化等问题。同时气候暖干化的趋势更加剧了森林需水与土壤供水之间的矛盾，危及区域水资源供给安全。如何利用有限水资源维持黄土高原人工林生态系统持续发展是目前该区生态建设的重要目标，而其核心就是土壤水分。因此，研究退耕还林的土壤水文效应及疏伐管理，在理论上有助于揭示人工林生态系统水源涵养机理，在实践上对于该区有限水资源利用，以及对人工林管理具有重要的现实意义。本论文以黄土高原人工林生态系统为研究对象，对人工林0~5.0 m土层的土壤水分进行了大面积调查研究，定量分析了不同人工林不同土层影响土壤水分分布的因素，研究了样带尺度下土壤干层分布特征及影响因素，动态监测并分析了林下植被和去除林下植被小区尺度土壤储水量的变化特征及其影响因素，通过分析小区尺度上层林木降水再分配过程土壤水分净输入（指除去冠层截留净输入土壤的水分）、地表径流和生长期剖面土壤储水量变化的基础上，根据水量平衡原理对林下植被的蒸散耗水特征及其影响因素进行了研究，同时结合生态疏伐管理研究了不同疏伐处理下人工林土壤水分平衡，所取得主要结论如下：1.评估黄土高原退耕还林土壤水分消耗及影响因素。人工林土壤含水量普遍低于农地，土壤储水量平均减少169.6 mm。3.0~4.0和4.0~5.0m土层土壤储水量比1.0~2.0、2.0~3.0 m浅土层要损失量最大，土壤储水量消耗随着土层深度增加而增加。不同降雨区土壤储水量消耗不同。降雨量> 550mm区域，土壤储水量损失的最高，为214.7 mm，450~550 mm区域土壤储水量损失195.7mm，< 450 mm区域土壤储水量减少的最少，仅为36.0 mm。土壤水分消耗与退耕前土壤水分、降雨量、气温和坡度呈显著正相关。2.评估影响人工林不同土层土壤水分空间格局的主导因素。不同类型人工林地土壤水分分布不同。土壤含水量表现为经济林>生态林>灌木，深层土壤水分变异性较大。降雨量和粘粒含量对不同土层土壤水分分布格局影响最大。随着土层深度增加，局部因素对生态林土壤水分影响较大，气象因素对经济林土壤水分影响较大，而在灌木地局部影响和气象因素差异不大。3.样带尺度下土壤干层的分布格局与影响因素。在垂直方向上，剖面土壤含水量逐渐减小，土壤干燥化严重。土壤干层平均厚度为289.1 cm，干层平均含水量为7.7%，干层起始平均深度为151.9 cm。不同降雨区土壤干层有较大的变异性，由湿润区到干旱区，土壤干层水分先减小后增加。环境因子解释的变异性对土壤干层总变异性的比例为38.0%。局部因素单独解释变异性比例（16.5%）大于气候因素单独解释的变异性比例（4.2%）4.沟道对坡面土壤水分时空变异性的影响。距沟道越远土壤储水量愈大，300 cm处样点可代表测定尺度下土壤储水量的平均值。在垂直方向上，切沟增大了土壤水分的变异性。不同植被类型下，土壤水分空间分布格局受植被类型主导，沟道、坡位、微地形等因素处于次要地位。5.评估人工林林下植被蒸散耗水。人工刺槐林地，穿透雨占林外降雨量比例约87.3%，其次为冠层截留占林外降雨量比例约为10.4%，茎干流最小约占林外降雨量比例的2.3%。观测期内上层林木蒸腾耗水量约为265.0 mm，林下植被蒸散耗水量约为120.5 mm，林下植被蒸散耗水量约占生长期森林耗水量的31.3%。6.生态疏伐对人工林土壤水平衡的影响。整个观测期内，疏伐40%和90%处理土壤水分分别亏缺82.4 mm和38.5 mm。随疏伐程度增加土壤水分消耗减小。同时随着疏伐量增加，林下植被蒸腾耗水增加52.4 mm。林下植被蒸腾的增加抵消了疏伐林分的水分蒸腾部分。综上所述，黄土高原大规模退耕还林消耗了深层土壤水分，土壤水分严重亏缺形成持久的土壤干层，对区域人工林生态系统产生深刻影响，同时林下植被蒸散耗水是人工林生态系统不可忽视的水分耗损项，对该区进行生态疏伐可以显著改变土壤水分循环过程。 |
| 英文摘要 | In recent years, the dramatic changes in vegetation has been made by large-scale farmland to forest on the Loess Plateau of China. However, the negative feedback between vegetation growth and soil water capacity has been developed due to irrational vegetation construction, which makes the formation of dried soil layers (DSL), the emergence of vegetation degradation and other ecological problems. Meanwhile, warming-drying trend exacerbated the contradiction between water use of forest and soil water supply, and caused safe supply of water resources in the region. To use the limited-water resources maintaining the sustainable development of artificial forest ecosystem on the Loess Plateau becomes an important goal of ecological environment construction in the region, and the core of the goal is soil water. Therefore, studying hydrological effect of returning farmland to forest and ecological thinning on the loess plateau of china, it is helpful to study the mechanism of soil-water conservation of artificial forest ecosystem in theory, and it is of great practical significance for the limited-water resources utilization and the management of forest in practice. In this paper, the soil water content (SWC) of 0 ~ 5.0 m soil layer was studied for the artificial forest on the Loess Plateau at large scale. The factors affecting the distribution of soil water in different soil layers were quantitatively analyzed. The characteristics of DSL and its influencing factors were analyzed along the transect scale. The characteristics and influencing factors of soil water storage (SWS) for understory vegetation and understory vegetation removal were dynamically monitored and analyzed at plot scale. Based on the analysis of the change of SWC in the process of redistribution of overstory (refer to the net input of soil water without canopy intercept), surface runoff and changes in SWS in the growing season, the characteristics of understory evapotranspiration (Eu) and its influencing factors were studied according to the principle of water balance. At the same time, the soil water balance of artificial forest ecosystem was studied under different thinning treatments. The main conclusions are as follows:1. Estimating regional losses of soil water and the influencing factors due to the conversion of agricultural land to forest inChina's Loess Plateau. SWC in artificial forest is generally lower than the agricultural land, SWS decreased by an average of 169.6 mm. The SWS capacity of 3.0 ~ 4.0 and 4.0 ~ 5.0 m soil layer is larger than 1.0 ~ 2.0, 2.0 ~ 3.0 m soil layer, and the losses of soil water increases with the depth of soil layer. SWS in different rainfall areas is different. Rainfall in the area of > 550 mm, the highest loss of soil water is 214.7 mm, the loss of soil water in the area of 450-550 mm is 195.7 mm, and in the area <450 mm is the least, only 36.0 mm. There was a significant positive correlation between soil water losses and initial SWS, rainfall, temperature and slope.2. To evaluate the dominant factors affecting the spatial pattern of soil water in different soil layers of artificial forests. SWC has great variation in different types of artificial forest different. The results showed economic forest (ENF)> ecological forest (ELF)> shrub land (SL), variability of deep SWC was great. Rainfall and clay content had the greatest influence on soil water distribution in different soil layers. With the increase of soil depth, the local factors had a great influence on the soil water distribution of ELF, while the meteorological factors had a great influence on the soil water distribution of ENF, but there was no significant difference between the local influence and the meteorological factors for SL.3. Spatial pattern and influencing factors of DSL along a south-north transect scale. SWC gradually reduced in the vertical direction, soil desiccation serious. The average thickness of DSL was 289.1 cm, the average water content of DSL was 7.7%, and the formed depth of DSL was 151.9 cm. There was a large variation of DSL in different rainfall areas. From dry area to arid area, SWC in DSL decreased and then increased. The contribution of environmental factors explained variability to DSL variation was 38.0%. Local factors alone explained the percentage of variability (16.5%) was greater than the climatic factors alone (4.2%).4. The effects of gully on spatial-temporal variability of SWC at hill-slope scale. The more distance to the gully, the greater SWS. The soil sampling site at distance of 300 cm could represent the average of the SWS at the measured scale. In the vertical direction, SWC had a great variability, which controlled by gully. Under the different vegetation types, spatial distribution pattern of SWC was dominated by vegetation types, gully, however, slope position, micro-terrain and other factors had a lesser influence.5. To evaluate Eu of artificial forest ecosystem. In the artificial forest of Robinia pseudoacacia, the percentage of throughfall accounted for about 87.3% of the rainfall outside the forest, interception by the canopy was followed, which accounted for about 10.4% of the rainfall, the percentage of stemflow accounted for about 2.3% of the rainfall. During the observation period, water use of Eo was about 265.0 mm, the water use of Eu was about 120.5 mm, and the percentage of the Eu was about 31.3% accounted for the water use of whole forest during the growing season.5. The effect of ecological thinning on soil water balance in artificial forest. During the observation period, soil water deficit were 82.4 mm and 38.5 mm for thinning 40% and 90%, respectively. Soil water deficit was less with increased thinning. With the increasing of the thinning for artificial forest, the transpiration of understory vegetation increased by 52.4 mm. The increased in transpiration of understory vegetation offset the increased part of evapotranspiration of the thinning.In summary, extensive afforestation on the Chinese Loess Plateau has led to decreases in deep SWC, and formed a persistent DSL due to soil water deficit, which has a profound effect on the artificial forest ecosystem, while the Eu couldn‘t be neglected, which is a great water loss part of artificial forest ecosystem. The ecological thinning for artificial forest can significantly change soil hydrological cycle process. |
| 中文关键词 | 退耕还林 ; 土壤水消耗 ; 尺度 ; 林下植被 ; 疏伐 |
| 英文关键词 | Afforestation Soil water loss Scale Understory vegetation Thinning Loess Plateau |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 土壤学 |
| 来源机构 | 中国科学院水利部水土保持研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287921 |
| 推荐引用方式 GB/T 7714 | 张晨成. 黄土高原退耕还林的土壤水分效应研究[D]. 中国科学院大学,2017. |
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